1. Field of the Invention
The present invention relates to a technique of preventing a destruction of data in a magnetic disc storage. More particularly, it relates to an improvement of a disc-drive apparatus which monitors an abnormality of a power supply voltage fed to a data writing unit magnetically coupled to a magnetic medium and, upon detecting the abnormality, forcibly cuts off the power supply voltage to thereby prevent a destruction of the data.
2. Description of the Related Art
In a known typical magnetic disc storage, a data writing unit for head selection and data writing, e.g., in the form of an integrated circuit (IC), receives a head select signal from a host controller in the write operation and selects one from among a plurality of magnetic heads. At the same time, the data writing unit receives a write gate signal from the host controller and drives a write amplifier provided therein at a constant current to cause a write current corresponding to the write data to flow through the selected magnetic head. In the write operation, where an abnormality occurs in that, e.g., a power supply voltage fed to the data writing unit is lowered, it is very difficult or almost impossible to ensure a reliable write operation.
To cope with this disadvantage, a prior art disc-drive apparatus monitors a power supply voltage fed thereto and, upon detecting an abnormality of the monitored power supply voltage, outputs a reset signal to a power supply voltage clamping circuit to thus clamp the power supply voltage, and forcibly cuts off the power supply voltage fed to a write amplifier provided therein, to thereby prevent a malfunction thereof. In this case, the disc-drive apparatus feeds the reset signal to a host controller and thus causes the write gate signal to be made OFF.
Nevertheless, a problem arises in a transient state existing until the functioning of the write amplifier is completely stopped based on the clamping of the power supply voltage. Namely, when a signal level of the head select signal fluctuates with a lowering of the power supply voltage in the transient state, the disc-drive apparatus is brought to a state equivalent to a state wherein the head select signal is changed or switched, because the functioning of the write amplifier per se has not completely stopped. Accordingly, in the transient period existing until the host controller receives the reset signal and responds thereto, to cause the write gate signal to be made OFF, a possibility occurs in that data of a medium corresponding to a head switched due to the malfunction is destroyed.
In view of this, there is a demand for an improvement of the conventional disc-drive apparatus to provide it with a function of completely preventing any destruction of data during the clamping of the power supply voltage.
Note, problems in the prior art will be explained in detail later in contrast with the preferred embodiments of the present invention.